1. Field of the Invention
The present invention relates to mobile ladders, and more particularly, to a mobile ladder having a floor lock.
2. Description of the Prior Art
Mobile ladders having floor locks used in warehouses or for maintenance use are well known. Examples of such mobile ladders are described in U.S. Pat. Nos. 1,439,388, Willett, 1922; 2,798,652, Easton, 1957; 2,923,373, Ledgerwood, 1960; 3,155,190, Borgman, 1964; 3,175,641, Mihalik, 1965; and 3,291,254, Mihalik, 1966.
The purpose for which such mobile ladders are used and the reason for a wheel or floor lock is well documented in these patents. In summary, the mobile ladder includes a frame on which a step ladder is provided at a permanently useful angle, and castor wheels on the frame for the purpose of moving the frame and ladder to any location on a given floor in a building. When it is required to mount the ladder, the floor lock is engaged so as to prevent the ladder from moving while a person is on the ladder and thereby possibly causing accidents.
The floor locks of present day mobile ladders appear to be of two types. In the Borgman, Ledgerwood, Easton, and both Mihalik patents, there is described a floor lock in which at least a wheel is movable in a vertical plane between a floor engaging position and a floor disengaging position where accompanying support members or stops would be engaging the floor preventing the mobile ladder from moving. In the other type of floor lock, reference can be made to the Willett patent as well as U.S. Pat. No. 2,897,910, Steely et al, 1959, referring to a service cart having a floor lock. In these patents, the castor wheels are fixed to the frame while a separate movable support member can be actuated to lift the frame off the floor, thereby lifting certain wheels which are fixed to the frame. All of the floor locks referred to in the above patents include floor lock linkage systems which are relatively complicated and which require a number of parts which, of course, must be maintained. Many of the patents use spring-loaded mechanisms which add to the complexity of the construction and can lead to unreliability of the devices.